The present invention relates to an air-spinning arrangement having an opening device for opening a sliver.
In connection with open-end spinning processes such as rotor spinning, a sliver is opened into individual fibers by means of an opening roller. For preventing fiber compressions in connection with air-spinning, or with open-end spinning methods, such as friction spinning, it is customarily desired that the fiber material can be continuously accelerated over the entire path from the feeding device of the opening roller to the yarn withdrawal device. In this way, the fibers remain stretched.
A spinning process is known from German Patent Publication DE 196 01 038 A1 in which several slivers are conducted to an opening roller. The opened fibers are removed from the opening roller by means of a perforated removal roller, to which suction is applied. The individual fibers are not to be slowed at the transfer points, but ideally are to be accelerated in order to prevent the compression of the fibers. The removal roller acts together with a friction roller. The fibers, while spinning, are withdrawn transversely in the conveying direction in the nip between the removal roller and the friction roller. A false twist is generated by the spin creation, which is turned out of the fiber structure downstream of the nip. In order that the fiber structure has stability, a pneumatic spin nozzle is arranged downstream of the nip. Fiber ends that have been released are to be wound around the fiber core in the spin nozzle. However, the release of fiber ends is made more difficult by the dissolving false twist. The yarn stability that can be achieved in this way is low.
German Patent Publication DE 196 10 960 A1 discloses a method for air-spinning, wherein slivers are also opened into individual fibers by an opening roller. Yarn formation occurs by means of a spinning device for twisting the yarn to be spun. A thin fiber fleece is to be formed from the opened individual fibers and the fibers of the thin fiber fleece are to be fed to a collecting surface extending transversely with respect to their direction of movement, from which they enter immediately thereafter into the spin device. In this case, the distance viewed over the working width, between the collecting surface and the previous fiber-conducting surface is not always constant. In connection with one embodiment, in which the collecting surface directly follows the opening roller, the fibers are hurled off the circulating combing elements and travel the distance to the collecting surface in an uncontrolled free flight. The fibers conveyed along with the combing elements can be located anywhere between the surface of the opening roller, or the base of a saw-toothed fitting, and the tip of the combing elements at a place that is mainly determined by accident. The release from the fittings of the opening roller takes place in free flight, wherein the distance traveled is a function of the initial position of the fibers in the fittings.
Free flight of the fibers to the collecting surface also takes place in the exemplary embodiment of German Patent Publication DE 196 10 960 A1, in which the collecting surface does not immediately follow the opening roller, but where the fibers are transferred from the opening roller to a removal roller, and are only fed to a collection surface from the removal roller. Viewed across the working width, the distance between the fiber-conducting surface of the removal roller and the following collecting surface is not constant. Thus, paths of different lengths for the fiber transfer result. The distance over which the fibers move in free flight can be relatively long. An uncontrolled free flight of the fibers holds the danger that a compression or random orientation of the fibers can result. This hampers the yarn formation, and lack of quality of the finished yarn occurs. The application of suction to the collecting surfaces leads to an additional use of air that, in spinning frames with a multitude of spinning stations, constitutes a considerable disadvantage.
German Patent Publication DE 197 46 602 A1, which defines the species, shows a spinning process in which slivers are opened by an opening roller, the individual fibers are taken over by a removal roller, and a thin fiber fleece is formed and combined on the removal roller. A slubbing-like fiber structure is intended to be created in the process, that is passed through a nip formed with the aid of the removal roller and fed to a pneumatically operating spinning nozzle. The combination of the thin fiber fleeces is achieved by means of an appropriate embodiment of the suction insert in the removal roller. The area of the removal roller to which suction is applied tapers in the conveying direction of the fibers. The combination of the thin fiber fleeces performed in this way only has a chance of success if a path of sufficient length is available for the combining. In order to obtain the required circumferential length, the combination of the thin fiber fleece has been parceled out to two successive suction rollers. Combining the thin fiber fleece in accordance with this process contains disadvantages since individual fibers can be sucked into the perforation of the removal roller and are not released at the edges of the area to which suction is applied as is required for functioning. They then remain attached to the removal roller in the form of so-called circulating fibers and often prevent other fibers from being released in the desired manner from the removal roller. Circulating fibers can result in yarn defects which are created in that the caught fiber is only released after several fibers have collected and adhere to it. The result is a slub in the yarn. Adhering fibers can also cause fiber windings on the removal roller and because of this can considerably interfere with the functioning of the spinning device, or can even stop it. A large consumption of suction air is created by the extensive areas to which suction is applied, in particular with two removal rollers to which suction is applied, which decisively interferes with the efficiency of the spinning process.
A friction spinning method is known from Japanese Publication JP (A) 3-15 2223, in which a belt is employed as the collecting surface. No speed conditions or distance settings are provided in this publication in connection with the working together of the individual elements. No air aspiration, wherein air is sucked off through the belt, can be seen, nor is it provided. Even though no additional extensive suction air consumption is created, the disclosed arrangement has disadvantages. The fiber structure formed from the collected fibers is given a twist by the friction belt, which goes counter to the use of the device in an air-spinning process, because the twisting interferes with air-spinning, and the yarn stability which can be achieved would be kept low. The friction belt clamps the fibers arriving at the collecting line, so that the withdrawal of the fiber structure, which is subjected to twisting, is made difficult.
It is accordingly an object of the present invention to improve the known arrangements for air-spinning.
According to the present invention, this object is addressed by an air-spinning arrangement comprising: an opening device having a feed device and an opening roller for opening a sliver into individual fibers; a perforated removal roller rotatable in a direction of revolution for receiving the opened fibers at a feeding zone adjacent the opening roller and transporting the opened fibers therefrom in the direction of revolution of the removal roller; a conveying device for transporting the fibers from the removal roller to a nip at a downstream located air-spin nozzle for forming a yarn, wherein the conveying device comprises a conveyor belt arranged downstream of the feeding zone and driven in axially parallel relation with the removal roller at a sufficiently close spacing to the removal roller for picking up the fibers from the removal roller by mechanical contact and deflecting the fibers by approximately 90xc2x0 for delivery to the nip.
In accordance with the present invention, the conveyor belt surprisingly neither imparts a twist to the fiber structure formed in the nip and consisting of fibers taken over from the opening roller nor does the withdrawal of the fiber structure entail any difficulties. Following the deflection by 90xc2x0, the fibers lie stretched and parallel in the strand-like fiber structure. This position of the fibers is maintained during their conveyance through the following nip to the air-spin nozzle, and makes possible very good spinning of the fiber structure by means of an air-spinning process.
No additional application of suction is required for the functioning of the conveyor belt as the collecting surface for the fibers. Therefore, corresponding additional suction air consumption is avoided, and the efficiency when using the air-spinning arrangement in accordance with the present invention is not hampered.
In connection with a conveyor belt that is arranged tangentially in relation to the removal roller, the transfer of the fibers from the removal roller to the conveyor belt is aided. An air flow coming from below is generated in the lower nip between the removal roller and the conveyor belt by means of applying suction to the perforated removal roller that aids in the release of the fibers from the removal roller.
If, as in one embodiment of the present invention, a sufficiently close spacing of 0.2 mm to 0.7 mm is selected as the smallest distance, on the one hand the surface of the conveyor belt is positioned close enough to the removal roller for picking up the fibers conveyed on the removal roller by means of a mechanical contact and to prevent the free uncontrolled flight of the fibers, on the other hand is the surface of the conveyor belt sufficiently far removed from the removal roller to prevent the application of a spin generated by friction to the fiber structure, or to make the fiber removal from the nip more difficult.
In another embodiment of the present invention, a conveyor belt with a microscopically roughened surface, or made of a material with a high coefficient of friction improves the pickup and conveyance of the fibers by the conveyor belt without interfering with the release from the conveyor belt.
In yet another embodiment of the present invention, a conveyor belt that is impermeable to air prevents undesired interference with the air flow directed to the nip from below and increases the dependability of the release process of the fibers from the removal roller.
In still yet another embodiment of the present invention, a layout of the conveyor belt drive mechanism wherein the speed of the conveyor belt is slightly greater than or equal to the circumferential speed of the removal roller aids in the prevention of compression of the fibers.
The air-spinning arrangement in accordance with the present invention permits the efficient and unhampered production of a yarn in accordance with the air-spinning process and overcomes disadvantages of known arrangements.
Further details of the present invention can be gathered from a non-limiting exemplary embodiment presented in the following description with reference made to the drawings.